VSC-HVDC transmission line faults location using active line impedance estimation

This paper describes the use of an active impedance estimation technique to accurately locate faults in a VSC-HVDC system transmission line. This method uses the power converters already installed in the HVDC system, without requiring any external additional hardware or intervention. The DC-link capacitor at the generator side is used to generate a voltage pulse in the DC line. The resulting voltage and current transients are Fourier transformed and used to estimate the impedance between the observation point and the fault location. This impedance is used to provide an initial estimation of the fault location which is compared with that obtained from an equivalent model of the transmission line. Through an iterative scheme the fault location and fault resistance are continually updated until an agreement is reached between measured and calculated impedances. Simulation demonstrates the effectiveness and reliability of the proposed method which achieves a fault location precision of tens of meters for line length of tens of kilometers. Also, the proposed method identifies the faulted line or if the fault is line to ground or two line to ground.